Hello , I a creating program in witch objects are stored in the namespace var in var.h. How do I make the var namespace available to more than one file without having redefinition errors ?

### var.h ###
namespace var
{ ... }
### main.cpp ###

#include "var.h" //multiple redefinition error 

...

### engine.cpp ###

#include "var.h" //multiple redefinition error 

...

### objects.h ###

#include "var.h" //multiple redefinition error 

...

It's not the namespace, it's the stuff in the namespace that gets redefined. Ideally you would put only declarations in a header and definitions in a separate implementation file. But you can help alleviate the problem with inclusion guards.

It's not the namespace, it's the stuff in the namespace that gets redefined. Ideally you would put only declarations in a header and definitions in a separate implementation file. But you can help alleviate the problem with inclusion guards.

can you give me an example of that ?

Assuming that your code was showing multiple files
including the same file indirectly

by adding the preprocessor line to the top of all of your .h files

#pragma once

you can ensure that no single file includes the same file twice.

well , I have 2 header files that include each other objects.h and vars.h. The #pragma once is causing var to ignore objects.h from being included ... So whats the solution for this , merge them ? or is there some other command that is used to combat this from happening ?

Edited 6 Years Ago by wwsoft: n/a

I have merged vars & objects but I get is error from this code

namespace var
{
    vector<game_object*> _objects_; //error , vector is included ... 
    vector<SDL_Surface*> _img_; //error
    vector<TTF_Font*> _font_; //error
    vector<Mix_Chunk*> _sound_; //error
    vector<Mix_Music*> _music_; //error
    

    bool quit=0;
    bool pause=0;
    int sound_volume=100;
    int music_volume=100;
}
### Error ###
error: expected constructor, destructor, or type conversion before ‘<’ token
error: expected constructor, destructor, or type conversion before ‘<’ token
error: expected constructor, destructor, or type conversion before ‘<’ token
error: expected constructor, destructor, or type conversion before ‘<’ token
error: expected constructor, destructor, or type conversion before ‘<’ token

---
darn cant edit my posts after 1/2 hour ...

I am using a different version of compiler so different errors but
have you scoped vector?
the std::

//var.h
#pragma once
#include <vector>
namespace var
{
std::vector<int *> vpi;
std::vector<double *> vdi
}

works for me.

works , but .... even with "#pragma once" on top Im getting

...
In function main
multiple definition of `var::_objects_
first defined here
In function main
multiple definition of var::_img_
first defined here
In function main
multiple definition of var::_font_
first defined here
In function main
multiple definition of var::_sound_
first defined here
In function main
first defined here|
In function main
multiple definition of var::quit
first defined here
In function main
multiple definition of var::pause
first defined here
...

obejcts.h

#pragma once

#ifndef OBJECTS_H_INCLUDED
#define OBJECTS_H_INCLUDED


....

using namespace std;

class game_object
....

class cpong1 : public game_object
....


namespace var
{
    vector<game_object*> _objects_;
    vector<SDL_Surface*> _img_;
    vector<TTF_Font*> _font_;
    vector<Mix_Chunk*> _sound_;
    vector<Mix_Music*> _music_;


    bool quit=0;
    bool pause=0;
    int sound_volume=100;
    int music_volume=100;
}

#endif // OBJECTS_H_INCLUDED

any advice ?

Assuming that in all your own .h you have #pragma once

If you rename _objects_ to _abcdefgh_1234
do you get the same error with "_objects_"
replaced with _abcdefgh_1234 ?

if not then you have two places where you have used the same function name and this needs to be fixed it could be var:: is used elsewhere

I always uses classes and don't use the using so as not to confuse
visio intellisense or risk polluting the namespace

I am not familiar with the SDL libraries that you are using
but I assume that you are trying to get some game to work
without using the windows api.

It might be missing something obvious... but there is a lot of
includes and code that are not being shown here and an equivalent
code for me does not give an error

works , but .... even with "#pragma once" on top Im getting

...
In function main
multiple definition of `var::_objects_
first defined here
In function main
multiple definition of var::_img_
first defined here
In function main
multiple definition of var::_font_
first defined here
In function main
multiple definition of var::_sound_
first defined here
In function main
first defined here|
In function main
multiple definition of var::quit
first defined here
In function main
multiple definition of var::pause
first defined here
...

obejcts.h

#pragma once

#ifndef OBJECTS_H_INCLUDED
#define OBJECTS_H_INCLUDED


....

using namespace std;

class game_object
....

class cpong1 : public game_object
....


namespace var
{
    vector<game_object*> _objects_;
    vector<SDL_Surface*> _img_;
    vector<TTF_Font*> _font_;
    vector<Mix_Chunk*> _sound_;
    vector<Mix_Music*> _music_;


    bool quit=0;
    bool pause=0;
    int sound_volume=100;
    int music_volume=100;
}

#endif // OBJECTS_H_INCLUDED

any advice ?

the vector _DEBUG_ and int pie I included is also included in the errors

This is All the messy code in objects.h is anything horribly wrong with it ?

are there any better ways to make vars available globally ?

#pragma once

#ifndef OBJECTS_H_INCLUDED
#define OBJECTS_H_INCLUDED

#include <SDL.h>
#include "SDL_image.h"
#include "SDL_ttf.h"
#include "SDL_mixer.h"

#include <cstdio>
#include <vector>
#include <iostream>
#include "engin.h"

using namespace std;

class game_object
{
    public:

    SDL_Surface* sprite;
    SDL_Rect rect;
    std::string type[3];//controller , group , name

    int x;
    int y;
    int z;
    bool dead;

    virtual void update()
    {
    }


    std::string get_type(int typen)
    {
        if (typen==0)
            return type[0];
        if (typen==1)
            return type[1];
        if (typen==2)
            return type[2];
    }

    SDL_Surface * get_sprite()
    {
        return sprite;
    }

    SDL_Rect get_rect()
    {
        return rect;
    }

};

class cpong1 : public game_object
{
    public:

    cpong1( int xx , int yy , int zz )
    {
        x=xx;
        y=yy;
        z=zz;

        type[0]="player"; //controller
        type[1]="pong"; //object group
        type[2]="cpong1"; //object
        dead=0;

        sprite=SDL_CreateRGBSurface(SDL_HWSURFACE, 16, 48, 8, 255, 255, 255, 255);
        SDL_FillRect(sprite, 0, (180,180,180));
        rect.w=sprite->w;
        rect.h=sprite->h;
        rect.x=x;
        rect.y=y;
    }

    virtual void update()
    {
        Uint8 *keystate = SDL_GetKeyState(NULL);
        if ( keystate[SDLK_UP] )
            y-=5;
        if ( keystate[SDLK_DOWN] )
            y+=5;

//            drip_rect_collide_all(rect,var::_objects_,0);

    }

    ~cpong1()
    {
        SDL_FreeSurface(sprite);
    }
};




namespace var
{
    vector<game_object*> _objects_;
    vector<SDL_Surface*> _img_;
    vector<TTF_Font*> _font_;
    vector<Mix_Chunk*> _sound_;
    vector<Mix_Music*> _music_;


    bool quit=0;
    bool pause=0;
    int sound_volume=100;
    int music_volume=100;
}

#endif // OBJECTS_H_INCLUDED

Edited 6 Years Ago by wwsoft: n/a

Use the extern keyword to introduce the variables inside the header (.h) files. Define these variables in their counterpart .cpp files.

For example, your header could be

#ifndef OBJECT_H_DEFINED
#define OBJECT_H_DEFINED

// file: object.h

// std::vector is needed in this header file
#include <vector>

// Introduce what is exposed by the 'var' namespace 
namespace var
{
    // You cannot have variables defined in a header file, which
    // is included by multiple .cpp files. So they need to be extern ...
    extern std::vector<game_object*> _objects_;
    extern std::vector<SDL_Surface*> _img_;
    extern std::vector<TTF_Font*> _font_;
    extern bool quit;
    extern bool pause;
    extern int sound_volume;
    // etc ...

    // An ordinary function declaration, no need for extern
    void ordinary_function();

    // A class declaration
    class some_class
    {
        // ctor
        some_class();
    };
}
#endif // ndef OBJECT_H_DEFINED

Then the .cpp file would be

// file: object.cpp

#include "object.h"
namespace var
{
    std::vector<game_object*> _objects_;
    std::vector<SDL_Surface*> _img_;
    std::vector<TTF_Font*> _font_;

    bool quit = 0;
    bool pause = 0;
    int sound_volume = 100;

    void ordinary_function()
    {
         // something here
    }

    // class definition ...
    some_class::some_class()
    {}
}

[EDIT]
The above is to demonstrate the basic idea of putting these things together, so given that there are e.g. SDL_Surface * and such, you also need the related headers for those included in proper places. But I hope that you get the basic idea though.

Edited 6 Years Ago by mitrmkar: ordinary_function()

Thank you ! I had been trying to work through that for a week :)

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